How best to overwrite a Javascript object method

Question

I'm using a framework that allows the include of JS files. At the top of my JS file I have something like:

<import resource="classpath:/templates/webscripts/org/mycompany/projects/library/utils.lib.js">

I want to override a fairly small method that is defined in the very large utils.lib.js file. Rather than make the change directly in utils.lib.js, a file that's part of the framework, I want to overwrite just one method. The utils.lib.js file has something that looks like:

var Evaluator =
{
   /**
    * Data evaluator
    */
    getData: function Evaluator_getData(input)
    {
          var ans;

          return ans;
    },
    ...
 }

I want to change just what the method getData does. Sorry for the basic question, but after importing the file which copies the JS contents into the top of my JS file, can I just do something like:

 Evaluator.getData = function Mine_getData(input)
                {
                  ...
                };

jfriend00 · Accepted Answer · 2011-09-12 01:06:01Z

3

Yes, you can just reassign that method to your own function as you have proposed with:

 Evaluator.getData = function Mine_getData(input)
 {
     ...
 };

This will successfully change what happens when the .getData(input) property is called.

edited Sep 12, 2011 at 1:06

answered Sep 12, 2011 at 1:00

jfriend00

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1 Comment

simbabque Over a year ago

How would you get to load the original function? Save it beforehand by going var foo = Evaluator.getData; and later in the new function calling foo()?

BenMorel · Accepted Answer · 2014-01-06 11:38:21Z

0

Yes you can.

However Evaluator is not a proper 'class'. You can't write var x = new Evaluator(); So you are not overriding, but just changing the variable getData. That's why we say that in JavaScript, functions are first-class citizen, treated like any variable.

edited Jan 6, 2014 at 11:38

BenMorel

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answered Sep 30, 2011 at 7:54

Nicolas Zozol

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